Symbology

Feature layer query

In this topic

# Feature layer query
This sample demonstrates how to query a feature layer via feature table.
<img src="FeatureLayerQuery.jpg" width="350"/>
## Instructions
The sample provides a search bar on the top, where you can input the name of a US State. When you hit search the app performs a query on the feature table and based on the result either highlights the state geometry or provides an error.

// Copyright 2016 Esri.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License.
// You may obtain a copy of the License at: http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific
// language governing permissions and limitations under the License.
using Esri.ArcGISRuntime.Data;
using Esri.ArcGISRuntime.Geometry;
using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Symbology;
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Threading.Tasks;
using System.Windows;
namespace ArcGISRuntime.WPF.Samples.FeatureLayerQuery
{
[ArcGISRuntime.Samples.Shared.Attributes.Sample(
"Feature layer query",
"Data",
"This sample demonstrates how to query a feature layer via feature table.",
"The sample provides a search bar on the top, where you can input the name of a US State. When you hit search the app performs a query on the feature table and based on the result either highlights the state geometry or provides an error.")]
public partial class FeatureLayerQuery
{
// Create reference to service of US States.
private string _statesUrl = "http://sampleserver6.arcgisonline.com/arcgis/rest/services/USA/MapServer/2";
// Create globally available feature table for easy referencing.
private ServiceFeatureTable _featureTable;
// Create globally available feature layer for easy referencing.
private FeatureLayer _featureLayer;
public FeatureLayerQuery()
{
InitializeComponent();
// Create the UI, setup the control references and execute initialization.
Initialize();
}
private void Initialize()
{
// Create new Map with basemap.
Map myMap = new Map(Basemap.CreateTopographic());
// Create and set initial map location.
MapPoint initialLocation = new MapPoint(-11000000, 5000000, SpatialReferences.WebMercator);
myMap.InitialViewpoint = new Viewpoint(initialLocation, 100000000);
// Create feature table using a URL.
_featureTable = new ServiceFeatureTable(new Uri(_statesUrl));
// Create feature layer using this feature table. Make it slightly transparent.
_featureLayer = new FeatureLayer(_featureTable)
{
Opacity = 0.6
};
// Create a new renderer for the States Feature Layer.
SimpleLineSymbol lineSymbol = new SimpleLineSymbol(SimpleLineSymbolStyle.Solid, Color.Black, 1);
SimpleFillSymbol fillSymbol = new SimpleFillSymbol(SimpleFillSymbolStyle.Solid, Color.Transparent, lineSymbol);
_featureLayer.SelectionColor = Color.Cyan;
_featureLayer.SelectionWidth = 4.0;
// Set States feature layer renderer.
_featureLayer.Renderer = new SimpleRenderer(fillSymbol);
// Add feature layer to the map.
myMap.OperationalLayers.Add(_featureLayer);
// Assign the map to the MapView.
MyMapView.Map = myMap;
}
private async void OnQueryClicked(object sender, RoutedEventArgs e)
{
// Remove any previous feature selections that may have been made.
_featureLayer.ClearSelection();
// Begin query process.
await QueryStateFeature(QueryEntry.Text);
}
private async Task QueryStateFeature(string stateName)
{
try
{
// Create a query parameters that will be used to Query the feature table.
QueryParameters queryParams = new QueryParameters();
// Trim whitespace on the state name to prevent broken queries.
string formattedStateName = stateName.Trim().ToUpper();
// Construct and assign the where clause that will be used to query the feature table.
queryParams.WhereClause = "upper(STATE_NAME) LIKE '%" + formattedStateName + "%'";
// Query the feature table.
FeatureQueryResult queryResult = await _featureTable.QueryFeaturesAsync(queryParams);
// Cast the QueryResult to a List so the results can be interrogated.
List<Feature> features = queryResult.ToList();
if (features.Any())
{
// Create an envelope.
EnvelopeBuilder envBuilder = new EnvelopeBuilder(SpatialReferences.WebMercator);
// Loop over each feature from the query result.
foreach (Feature feature in features)
{
// Add the extent of each matching feature to the envelope.
envBuilder.UnionOf(feature.Geometry.Extent);
// Select each feature.
_featureLayer.SelectFeature(feature);
}
// Zoom to the extent of the selected feature(s).
await MyMapView.SetViewpointGeometryAsync(envBuilder.ToGeometry(), 50);
}
else
{
MessageBox.Show("Retry your query with a valid state name, like 'California'.", "State not found!");
}
}
catch (Exception ex)
{
MessageBox.Show("An error occurred.\n" + ex, "Sample error");
}
}
}
}